1. Field of the Invention
The present invention relates to a re-imaging optical system which causes the spatial image from an objective optical system to be re-composed under a specified magnification. The system is suitable for a device which composes a spatial image with a microscope objective lens.
2. Description of Related Art
In recent years, a system has been known where the composing of images formed by microscope objective lenses is achieved using imaging devices such as CCDs and the like. The imaging device is positioned at the primary imaging plane of the microscope objective lens. This type of system offers the advantage that the system itself can be easily manufactured and designed. However, because it is preferable to have a small imaging device, the system encounters a problem that the visual field ratio becomes smaller even though the visual field number for the microscope tends to expand.
Therefore, in recent years re-imaging optical systems have been used which re-compose the spatial image formed by the microscope objective lens under a specified magnification on an imaging device. However, with the above re-imaging optical system, the problem exists that the object image on the imaging device is inferior compared to systems where the imaging device is positioned on the primary image plane of the microscope objective lens. This inferiority is due to aberrations in the re-imaging optical system. Increasing the number of lens component pieces in order to improve the optical performance of the re-imaging optical has been attempted. However, when performance is enhanced, the re-imaging optical system becomes longer. Thus, re-imaging optical systems have problems associated with increasing of the overall size of the system.